When observing return flow downstream of a fuel regulator through a transparent fuel line, the Applicant has detected bubble formation. In earlier tests when the return line was connected directly to a high pressure fuel pump inlet, the pump began to fail just after 15 hours of operation. It is suspected that the pump failure was due to bubbles resulting in some kind of cavitation erosion of the pump. The Applicant had then determine that the gas bubbles consist of high volatile components of the fuel, not air or vapors. The gas bubbles can occur after the dissipative orificing process of the fuel regulator.
Accordingly, there is a need to reduce or preferably eliminate the formation of the gas bubbles in order to ensure a long life of a high pressure fuel pump.